The invention generally relates to image pick-up modules, particularly for an installation in an endoscope. More specifically, the invention relates to an image pick-up module, comprising an electronic image sensor, a first circuit board, a second circuit board, and a cable.
The invention further relates to a method for producing an image pick-up module.
An electronic image pick-up module according to the invention is preferably used in an endoscope, particularly in a flexible endoscope, the image pick-up module being arranged in the distal end of the endoscope shaft. Such an endoscope or video endoscope, respectively, is described, for example, in U.S. Pat. No. 5,754,313. Other illustrative uses of the image pick-up module according to the invention are the installation in a microscope, a medical miniature camera, an exoscope etc.
An image pick-up module generally comprises an electronic image sensor which converts light incident on it into electrical signals. Generally, such electronic image sensors are constructed in CCD or CMOS technology.
At present, miniaturized image sensors can be obtained among which those are preferred which are produced in TAB (Tape Automated Bonding) technology. Such image sensors have contact fingers arranged in at least one row, usually in two rows on opposite narrow sides of the image sensor, which extend approximately perpendicularly to the light receiving side of the image sensor away from the latter in the image pick-up module.
The use of an image pick-up module for an endoscope in which the image pick-up module is installed into the distal tip of the endoscope shaft necessitates a miniaturized constructional size of the image pick-up module. However, the production of a miniaturized image pick-up module is afflicted with technical problems, especially with regard to the assembling of the arrangement of the image sensor, circuit board and cable.
In the prior art, various constructions of image pick-up modules have been described which, however, do not satisfactorily solve the technical problems in the assembling of the components of the image pick-up module.
In the document EP 2 018 043 A1, an image pick-up module is shown in its FIGS. 4a and 4b which has two circuit boards which are arranged behind one another in a direction perpendicular to the light-receiving surface of the image sensor. The first circuit board, seen from the image sensor, is here equipped with electronic or electrical components. The second circuit board which is arranged on the side of the first circuit board facing away from the image sensor is used for terminating the multi-wire cable. For this purpose, the second circuit board has a plurality of through holes into which the individual wires of the cable are inserted. The ends of the wires are here located approximately on the inner surface of the second circuit board which is constructed to be U-shaped overall. In the assembled state, the contact fingers of the image sensor encompass the second circuit board on its rear so that the contact fingers electrically conductively contact the second circuit board. Due to the U-shaped construction of the second circuit board, the second circuit board is in electrically conductive contact with the first circuit board via leads which, however, is difficult with a miniaturized construction of the two circuit boards and, in particular, is not suitable for an automated assembly by means of a robot.
In the document mentioned above, in a further illustrative embodiment, an image pick-up module which only has a single circuit board is shown in FIGS. 7a to 7c there. This circuit board has through holes through which the wires of the cable are passed, the wires being brought out of the surface of the circuit board facing the image sensor with their wire jackets and being bent over in order to bring the ends of the wire cores, after having been stripped, into electrically conductive contact with the circuit board. In this embodiment, the problem is that the ends of the wires must be stripped so that the wire cores can be soldered onto the surface of the circuit board facing the image sensor. For this reason, this image pick-up module is also not suitable for an automated assembly by means of a robot.
From the document EP 1 659 780 A1, a further image pick-up module is known which has a single circuit board which is both equipped with electrical or electronic components and used for terminating the multi-wire cable. The circuit board is constructed to be U-shaped or with a notch in the surface facing the image sensor. In this image pick-up module, the at least one electronic component is in electrically conductive contact with the circuit board by means of conductor leads which are run three-dimensionally in the space created by the U-shaped construction or by the notch, respectively. Such “air wiring” of the components of the image pick-up module is also not suitable for automatic production, especially not for an automatic production by means of a robot. The wires of the cable are contacted on the rear of the circuit board in this known image pick-up module.
In the document WO 00/72744 A2, an image pick-up module is described, the circuit board of which is formed from a one-piece plate foldable along flexible connecting sections, which plate can be folded to form a cube-shaped, cross-sectionally essentially U-shaped body. The circuit board body has in its folded state two sections essentially extending transversely to the image sensor and spaced apart, and a third space which extends essentially in parallel with the image sensor. Such an image pick-up module, too, is not suitable for automatic assembly of the individual components of the image pick-up module.
From document U.S. Pat. No. 6,494,739 B1, an image pick-up module is known which has a connecting piece with which the image sensor and a control circuit board are connected and which is used for electrically contacting a multi-wire cable. The wires of the multi-wire cable are fixed on the connecting piece in lateral indentations in the form of grooves which are metallized, and put in contact with the metallizations. The control circuit board with the image sensor is also in electrical contact with the connecting piece via metallizations. In a further illustrative embodiment in this document, the connecting piece is constructed of two plane-parallel plates, the plate facing away from the image sensor being used for electrically contacting the shields of the individual wires of the multi-wire cable and the plate facing the image sensor being used for contacting the signal conductors of the wires of the multi-wire cable. Here, too, there are on the two plates laterally, that is to say on their narrow sides, groove-like indentations for accommodating the shields or the conductors, respectively. The connecting piece does not have any through holes for passing through the wires of the multi-wire cable.
A further image pick-up module is known from the document US 2004/0263680 A1. In one embodiment described there, two plane-parallel circuit board parts are present which are spaced apart comparatively far from one another in the longitudinal direction of the image pick-up module. The wires of a multi-wire cable are partially in electrical contact with the underside of the circuit board part facing away from the image sensor, are partially passed through holes in this circuit board part and are in electrical contact with the latter as air wiring, bridging the distance from the circuit hoard part facing the image sensor.
Apart from the lacking suitability of the known image pick-up modules for automated assembly of the components of the image pick-up module, the known image pick-up modules have the further disadvantage that the image pick-up modules can only be subjected to a functional test when they are completely assembled, i.e. when the image sensor is also in electrically conductive contact with the circuit board or circuit boards. If, however, the contact arrangements and wiring arrangements of the circuit board or of the circuit boards are faulty, the entire image pick-up module including the expensive image sensor is unusable. In the known image pick-up modules, there is thus an undesirably high rejection rate of image sensors operating correctly per se.
In the known image pick-up modules, the wires of the multi-wire cable must be stripped individually before they are soldered onto the at least one circuit board, and cut to the correct length. In this context, the individual wires must end as shortly behind the cable root as possible, so that the constructional length of the entire module is as small as possible. This requirement complicates the stripping and trimming of the cables extremely and also renders this process very time-consuming.